California’s Invaders: Red-Eared Slider

(Trachemys scripta elegans)

General Description

Red-eared sliders are medium-sized freshwater turtles. Their top shell (carapace) and skin are olive to brown in color with yellow stripes. Their bottom shell (plastron) is usually yellow, although sometimes brownish orange, and has dark spots within the center of each shell plate (scute). Red-eared sliders can typically be distinguished by the thick red stripe behind each of their eyes, although some individuals lose their colorful skin and shell stripes over time and appear dark overall (melanistic). Unlike the smooth-edged shell of California’s native western pond turtle (Actinemys marmorata), the marginal (outer carapace) scutes of red-eared sliders are serrated or slightly forked in appearance. Male sliders have thick tails, elongated front claws, and are usually smaller than females. Adult red-eared sliders can range from approximately 5 to 11 inches in length. In captivity, they can live for up to 40 years or up to 20 years in the wild.

Current Distribution

Red-eared sliders
have been introduced into numerous counties throughout California including, but not limited to: Butte, Contra Costa, Kern, Lake, Los Angeles, Marin, Riverside, Sacramento, San Diego, San Luis Obispo, San Francisco, Santa
Barbara, Santa Clara, Shasta, Tulare, Ventura, Yuba, and Yolo counties. The native range of red-eared sliders includes the Mississippi Valley from Illinois to the Gulf of Mexico and extends
as far east as West Virginia and as far west as eastern New Mexico. Red-eared sliders have been introduced to many areas of the United States outside of their native range, as well as to other countries and are listed as one of the world's worst 100 invasive species.

Habitat Preference

Red-eared sliders occupy a variety of natural freshwater habitats, including streams, rivers, ponds, lakes, swamps, and marshes. They can also be found in manmade habitats such as ditches, canals, and park lakes/ponds. Red-eared sliders prefer slow-moving waters that have soft bottoms and contain an abundance of aquatic vegetation and basking sites. Red-eared sliders are often found in close proximity to urban areas due to higher incidents of pet releases.

Pathways

Red-eared sliders were originally, and continue to be, introduced to new areas primarily through the domestic and international pet trade. More than 52 million individual sliders were exported from the United States to international markets between 1989 and 1997. Pet sliders are typically introduced into the wild by escaping or being released by their owners. Red-eared sliders have also been introduced to new areas during transport for the commercial (live) food trade, and through intentional, ceremonial releases by some cultures and religions.

Impacts

Introduced red-eared sliders compete with native species for food and habitat. For example, in California and the other Pacific states, sliders compete with native western pond turtles for food, egg-laying sites, and basking sites. Red-eared sliders are also vectors of disease and can transmit parasites to native animal species, as well as the bacteria Salmonella to humans. The sale and distribution of viable eggs and all small turtles (shell length less than 4 inches) was banned, excepting educational and research purposes, in the United States in 1975 after public health investigations showed that small turtles were a major source of human Salmonella infections. Over time, the extensive use of antibiotics within turtle hatcheries has resulted in the development of antibiotic-resistant strains of Salmonella, further exacerbating the threat to humans, if spread. Introduced populations can expand rapidly, with female red-eared sliders able to lay up to 6 clutches per year, each containing up to 30 eggs.

Actions Taken if Found

A valid sportfishing license is required to take RES, though there is no limit per person. Please do not take live RES from the environment unless you are prepared to keep it in captivity for the remainder of its lifespan. If you have a RES you can no longer care for, give it to a friend or contact your local shelter or reptile rescue organization. Please do not release or relocate RES, as it is illegal to place, or cause to be placed, any aquatic plant or animal into the waters of the state (FGC sec. 6400). Restoration projects or removal efforts should refer to the AVMA Guidelines for Euthanasia of Animals for information on humane methods of euthanasia.

If you observe this species in California and would like to record your observation for tracking purposes, you may report your sighting to the CDFW Invasive Species Program online, by email to Invasives@wildlife.ca.gov, or by calling (866) 440-9530.